Endogenous proteolytic enzymes provide a variety of useful functions, including the degradation of invading organisms, antigen-antibody complexes, and certain tissue proteins that are no longer necessary. The serine proteases comprise a large family of enzymes that use an activated serine residue in the substrate-binding site to catalytically hydrolyze peptide bonds. Typically, this serine residue can be identified by the irreversible reaction of its side chain hydroxyl group with diisopropylfluorophosphate. Serine proteases participate in carefully controlled processes, such as blood coagulation, fibrinolysis, complement activation, fertilization, and hormone production. These proteases are utilized in a variety of diagnostic and therapeutic contexts, and as industrial enzymes.
Normally, serine proteases catalyze limited proteolysis, in that only one or two specific peptide bonds of the protein substrate are cleaved. Under denaturing conditions, serine proteases can hydrolyze multiple peptide bonds, resulting in the digestion of peptides, proteins, and even autolysis. Several diseases are thought to result from the lack of regulation of serine protease activity, including emphysema, arthritis, cancer metastasis, and thrombosis.
For example, human tryptase is a serine protease with trypsin-like proteolytic activity (see, for example, Numerof, et al., Exp. Opin. Invest. Drugs 6:811 (1997); Chan, et al., Prot. Express. Purif. 15:251 (1999); Elrod and Numerof, Emerging Therapeutic Targets 3:203 (1999)). Tryptase is almost exclusively found in the secretory granules of mast cells, and the enzyme is released along with heparin and histamine upon mast cell activation in inflammatory response. In humans, tryptase has been established as an important mediator of airway response and is implicated in increasing the magnitude of broncoconstriction in asthma. In addition, tryptase has been shown to stimulate cytokine production, and exhibit mitogenic effects in a variety of cell types, and therefore, the enzyme may also contribute to the hyperplasia and fibrotic changes observed in diseases such as asthma. Animal model studies and clinical studies have shown that tryptase inhibitors are effective in reducing asthmatic response to exposure of antigen, and in blocking the mitogenic effects described above.
Human tryptase has also been implicated in activities such as cleaving fibrinogen α and β chains, collagen IV, gelatinase, and fibronectin. Accordingly, the enzyme is implicated in the inhibition of coagulation and in tissue remodeling in the lung and other tissues. Moreover, tryptase is shown to cleave calcitonin gene-related peptide, which is a potent vasodilator, and hence tryptase may potentiate gastric ulceration or increase cutaneous neurogenic inflammation, and promote smooth muscle contraction. In addition, tryptases are implicated in matrix degradation, wound healing and tumor metastasis.
Therefore, the discovery of a new serine protease fulfills a need in the art by providing a new composition useful in diagnosis, therapy, or industry.